This invention relates to an image forming apparatus, and more particularly to an image forming apparatus suitable for recording on a recording medium an optical information inputted through a solid image-pickup element.
An electrophotographic copying machine has been conventionally well known as an image forming apparatus for forming an image on a recording medium. In such a copying machine are mainly adopted one of two copying processes, one of which is a process for collectively exposing a photosensitive layer on a photosensitive drum to an original image light to form an optical latent image on the layer, and the other of which is a process for beforehand storing an original image as a digital bit map information in a memory and then exposing a photosensitive layer on a photosensitive drum while scanning the layer with a laser beam in accordance with the bit map information, thereby forming an optical latent image on the layer.
In both of the above two processes, toners are directly coated on the photosensitive layer serving as a latent image forming surface to develope the latent image, that is, the latent image forming surface for forming a latent image thereon is identical to a developing surface for developing the latent image thereon. In general, the photosensitive layer comprises a photosensitive material formed of a semiconductive material, and thus is liable to be damaged. Accordingly, the direct coating of the toners on the photosensitive layer frequently causes the surface of the photosensitive layer to be deteriorated during a developing process for supplying toners or ink to the photosensitive layer and a cleaning process of cleaning the photosensitive layer after the developing process.
Particularly, in the latter process inlcuding a conventing operation of the latent image into the bit map information, an original is scanned with light and an image light reflected from the original is inputted by a solid image-pickup element such as a CCD (charge-coupled device) or the like to obtain an electrical image signal corresponding to the image light, which is once stored in a bit map information in a memory. A laser beam is modulated in accordance with the image signal and then is irradiated to the photosensitive layer on the photosensitive drum, that is, the surface of the photosensitive layer is scanned with the modulated laser beam to form an optical latent image on the photosensitive layer. Thereafter, the photosensitive layer having the optical latent image thereon is coated with toners to obtain a toner image, which is transferred to a recording medium (sheet), and finally a visible image corresponding to the original image is recorded on the recording medium. In this process, however, an exposing process for scanning the photosensitive layer with light is further required separately from a process for scanning the original with light, and therefore more time is required for recording a visible image on a recording medium. In addition, at least two exposure systems each for individually scanning each of the original and the photosensitive layer with light must be equipped with the apparatus. Accordingly, the apparatus itself is complicate in construction and a cost thereof is increased.